It looks like Elon Musk and his friends at Solar City are at it again. First, there was the Tesla electric car. Then came solar energy provider Solar City. Then came the financial innovation of bonds backed by solar power. Now they appear to be combining all of these, with Solar City offering commercial energy storage systems based on batteries produced by Tesla Motors.

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The batteries, which are "about the size of a small refrigerator," were originally developed to store solar energy during periods of cloud cover or darkness, which, of course, they certainly can do.

But the leaders at SolarCity saw another, perhaps larger opportunity—providing short term storage for buildings to reduce their peak power demands at the time of day when power is most expensive. People in the industry call this "load leveling," and it not only benefits customers, but it benefits the utility and the environment as well by reducing the need for inefficient and dirty "peaker plants" that are often used to fill in supply gaps during the busiest times of the day.

SolarCity’s new system is called DemandLogic and it combines the battery capacity with a solar array and software that responds to the change in both rates and demand charges throughout the day for commercial customers, balancing those with the array’s production and the building’s demand for power.

Lyndon Rive, SolarCity’s chief executive, says that the systems would also provide backup power and a working solar array during utility outages. The vision of this system is not to provide independence from the grid, though it would help to maintaining grid stability as more customers move into solar.